This invention relates to the resuscitation of cardiac arrest victims.
Cardiopulmonary resuscitation (CPR) is a well known and valuable method of first aid. CPR is used to resuscitate people who have suffered from cardiac arrest after heart attack, electric shock, chest injury and many other causes. During cardiac arrest, the heart stops pumping blood, and a person suffering cardiac arrest will soon suffer brain damage from lack of blood supply to the brain. Thus, CPR requires repetitive chest compression to squeeze the heart and the thoracic cavity to pump blood through the body. Very often, the victim is not breathing, and mouth to mouth artificial respiration or a bag valve mask is used to supply air to the lungs while the chest compression pumps blood through the body. The methods of providing oxygenated airflow to the lungs are referred to as ventilation.
It has been widely noted that CPR and chest compression can save cardiac arrest victims, especially when applied immediately after cardiac arrest. Chest compression requires that the person providing chest compression repetitively push down on the sternum of the victim at 80-100 compressions per minute. CPR and closed chest compression can be used anywhere, wherever the cardiac arrest victim is stricken. In the field, away from the hospital, CPR may be accomplished by ill-trained by-standers or highly trained paramedics and ambulance personnel.
When a first aid provider performs chest compression well, blood flow in the body is typically about 25-30% of normal blood flow. This is enough blood flow to prevent brain damage. However, when chest compression is required for long periods of time, it is difficult if not impossible to maintain adequate compression of the heart and rib cage. Even experienced paramedics cannot maintain adequate chest compression for more than a few minutes. Hightower, et al., Decay In Quality Of Chest Compressions Over Time, 26 Ann. Emerg. Med. 300 (September 1995). Thus, long periods of CPR, when required, are not often successful at sustaining or reviving the victim. At the same time, it appears that, if chest compression could be adequately maintained, cardiac arrest victims could be sustained for extended periods of time. Occasional reports of extended CPR efforts (45-90 minutes) have been reported, with the victims eventually being saved by coronary bypass surgery. See Tovar, et al., Successful Myocardial Revascularization and Neurologic Recovery, 22 Texas Heart J. 271 (1995).
In efforts to provide better blood flow and increase the effectiveness of bystander resuscitation efforts, chest compression devices capable of performing the tasks of the basic CPR procedure have been proposed and used. Our own modular CPR device, described in our co-pending U.S. patent applications Ser. Nos. 08/922,723 and 09/087,299 provide for circumferential chest compression performed by a battery operated motor and clutch assembly. The chest compressions are accomplished automatically after installation and initialization of the system. The devices are designed for use by both untrained and trained operators, so that they may be used on patients as quickly as possible. It is intended that any bystander recognizing a fallen patient will be able to gain access to a nearby device, install the device, and initiate the operation of the device to commence chest compression and patient monitoring.
Our CPR devices described in our co-pending applications Ser. Nos. 08/922,723 and 09/087,299 also incorporate an automatic emergency defibrillator. Defibrillation is a well known technique for restoring normal heart rhythm to a patient who is in cardiac arrest due to ventricular fibrillation or ventricular tachycardia. It involves attaching electrodes to the patient and applying a large electrical shock to the patient. Defibrillation can resuscitate a large class of cardiac arrest patients, and its success is enhanced by application of the shock early in the resuscitation effort. A minute or so of chest compression also enhances the effectiveness of defibrillation shocks in reviving the patient.
Recently, automatic emergency defibrillators (AED) have been installed in controlled areas such as airplanes, where the presence of trained operators and secure access to the AED can be maintained. The practice of installing AED""s in controlled areas is sometimes referred to as Public Access Defibrillation. However, laws in most jurisdictions forbid installation of the devices without maintenance of a number of trained operators in the controlled area and oversight of the program maintenance by a doctor.
Our co-pending application Ser. No. 09/100,840 provides a control system for operating an automatic defibrillator and an automatic chest compression device in coordination with each other to enhance the effectiveness of the resuscitation. The device also provides electro-stimulation for electroventilation, electrocounterpulsion, abdominal binding and glottic closure, all coordinated with the chest compression device to effect electrostimulation at various points in the compression cycle.
The public access CPR and AED device described below is intended to be installed in public areas where access is readily available to bystanders, first responders, EMT""s and doctors. However, it is not necessary, nor desirable, to permit full access of the device to the entire range of people who might desire or require access since some users will not be properly trained to supervise the device""s operation. To control and thus permit the optimal degree of access to the system, a tiered access system is used to control physical access and functional enablement of the system. Physical access means access to the device itself, and/or access to certain accessories used for patient treatment in conjunction with the device that may be stored in the device or with the device (ET tubes, venous access kits, laryngoscopes, drugs, etc.). Functional enablement refers to the system allowing operation of certain functions, such as chest compression, alteration of setpoints, application of defibrillating shock, etc. Thus, the system must be told (or determine for itself) that it is permitted to initiate a therapeutic mode before it does so. One mechanism for differentiating the type of user accessing the device is through the identification subsystem sensors, since, for example, only trained personnel are xe2x80x9ckey holdersxe2x80x9d (as described in further detail below in reference to FIG. 2.)
The intended models of use for these systems include installation in hospitals and ambulances, and widespread installation in public areas such as workplaces, shopping centers, athletic facilities and stadiums, and even in homes of patients with an identified high risk of cardiac arrest. The devices may be installed in hospitals and ambulances without concern about the level of training for the expected user, because the expected user will be a highly trained operator such as a physician, nurse or emergency medical technician. These trained users can be expected or required to have the expertise necessary to supervise and administer all phases of the resuscitation protocol. However, because installation and activation within minutes of the onset of cardiac arrest is critical to saving a patient""s life, it is desirable to allow the device to be deployed by untrained bystanders or minimally trained first responders, and permit trained first responders and untrained bystanders to operate the device in safe modes. The system reserves physical access to advanced equipment and/or functional enablement of advanced modes which may present some danger to the patient for trained first responders. The system may have additional treatment modules, such as drug delivery equipment, that should only be used by expert operators, and the system prohibits access to these modules to all but identified expert operators. Trained first responders and expert operators may identify themselves to the system through the use of access cards, identification numbers or access codes, while the system may assume lack of identification indicates use by an untrained bystander. In all instances of use, the system initiates communications with a remote medical center, where operator identity may be confirmed and the level of access and enablement of the system may be adjusted remotely.